Electromagnetic security system

ABSTRACT

A security system is described wherein radio frequency or microwave radiation of high intensity is used to disable or trigger denotation of explosive devices in a controlled environment. The electromagnetic radiation transmitted from a generator is imposed on a circuit creating a voltage spike in the circuit of greater magnitude than the components in the circuit are capable of handling, resulting in damage to active or passive circuit components, or to cause the circuit to fire in a controlled environment. The invention acts to disable or cause premature detonation of concealed devices.

BACKGROUND OF THE INVENTION

The present invention relates generally to security devices used tocheck baggage or shipping containers. Presently used devices used forinspection include x-ray imaging devices used to screed baggage inairports. The invention provides a security function by usingelectromagnetic radiation to disrupt the performance of electronicdevices or to make them detonate prematurely in a controlled area.

In providing air travel security, it is desirable to screen baggage,cargo, and any other items that are carried in aircraft. Current x-rayscreening techniques are based on irradiation of cargo and baggage withx-rays, which pass through materials of low density and are absorbed bymaterials of high density, creating of an image of the cargo thatreflects density and atomic number differences. Operators are trained toread x-ray images which indicate high density objects, metals, andsuspicious shapes; but, with the wide range of explosive devicesavailable today, error in interpreting the x-ray can result in failureto detect an explosive device, which has disastrous safety consequences.In addition, x-ray scanning is slow and tedious, as only a thin beam ofx-rays is used to scan the cargo in creation of the x-ray image. As aconsequence, at present, air cargo is only checked at random; explosivedevices can easily be concealed within a closed container to destroy aplane in flight. Since methods for explosive screening are timeconsuming, labor intensive, and not specific to explosives, only a smallfraction of the total volume of cargo that is shipped on airplanes isactually screened for explosive devices, which constitutes a seriousdeficiency in airplane security. There are other applications of theinvention where a recipient of cargo, baggage, or other items desiresthat such items be screened for the presence of explosive devices; thiscan include virtually any industry that handles or receives packageditems such as the postal service, Federal Express, secure areas,military bases, or government entities that may be targets.

Electromagnetic radiation (EM) of high intensity is capable ofdestroying electronic and electrical components. An example of anapplication of intense EM waves pertinent to the present invention isthe use of high power microwave and radio frequency (RF) electronicwarfare weaponry employed by the US Department of Defense to destroyenemy communications, weapons systems, and command centers. Such weaponsuse various methods of generating high powered EM waves, such asexplosively pumped flux compression generators, in order to damage ordestroy targeted electronic equipment. Typically, such munitions canonly be used once, generating high powered EM waves, usually microwaves,which induce voltage spikes in targeted electronics similar to alightning strike. The magnitudes of the induced voltages are far greaterthan the maximum rated voltages of the electronics resulting in failureor damage to individual transistors, capacitors, or other componentsintegral to the operation of the device. With reference to experimentswith high power EM waves, analytical analysis and harmonic balancednonlinear simulations suggest that device destruction be due to largedrain-gate voltage swing that exceeded the breakdown voltage under highRF drives. Results of high powered microwave damage to specificelectronic components have been observed and recorded in otherexperiments.

Aside from the operation of electromagnetic weapons systems, high powercontinuous or pulsed RF or microwave radiation from devices that are notweapons systems can cause damage to electronics. The action of such a RFor microwave generator is to produce a traveling EM wave that induces avoltage on any conductor that intercepts the wave. Any conductor acts asa receiving antenna converting the EM wave into a voltage.

An antenna, in its simplest form, that generates microwaves coupled toan axial vircator high power microwave source would be comprised of acylindrical waveguide tapered outward into a conical horn structure, acathode, and an anode. High velocity electrons emitted from the cathodeand not flowing to the anode create and area known as a virtual cathode.The electrons in the virtual cathode area oscillate at microwavefrequencies through the conical waveguide, which can be tuned to aresonant frequency yielding high power microwaves. Power levels achievedin vircator experiments range from 170 kiloWatts to 40 GigaWatts.Furthermore, the directivity of high power microwaves has been studiedand the output from an axially extracted vircator has been found to bewithin 20° of 0° vertical and horizontal reference planes, whichindicates applications to directional scanning, pertinent to theinvention at hand.

The voltage spikes from the EM waves may disable electronic componentsin several ways. First, active semiconductor devices, including bipolarand field effect transistors, diodes, and silicon controlled rectifiers,have maximum voltage ratings which cannot be exceeded without destroyingor impairing the function of the device. The failure of a semiconductordevice through this mechanism is sometimes referred to as “junctionbreakdown”. Transistors and other active semiconductors are sensitive toexcessive reverse biasing, which is also capable of destroying thedevice. The imposition of a large voltage transient by an EM wave caneasily destroy active devices through the mechanism of exceeding thevoltage specifications of the device. A second mechanism of disablingelectronic circuits is destruction of passive electronic devices such ascapacitors, resistors, and inductors through inducing a voltage largerthan the breakdown voltage of the device, which can create a permanentconductive channel, defeating the purpose of the device. The breakdownof dielectrics along the surface of an insulator is referred to as“flash-over”. Melting and shorting out of components can take place as aresult of imposition of high intensity EM waves as well, both of whichresult in the malfunction of the electronic device as a whole.Microwaves can enter a shielded electronic device in what is referred tohere as, the “front door” or the “back door”. Entering through the frontdoor means that the EM waves induce voltage spikes in the circuit bymeans of an antenna, cable, port, or power supply main originallydesigned for communication, transmission of signals, or electricalcontact with components outside the shielding. The action of the highpower EM waves in the case of front door operation can take placethrough destruction of the function of the first stages of amplificationof the device or with any component of the device that is wired to theantenna, cable, port or power supply main capable of generating anelectromotive potential in response to irradiation with EM waves.Entering through the “back door” means that the EM waves induce voltagespikes by entering the enclosure through cracks, screws, fittings, loosewires, etc, not specifically intended for communication, signaltransmission, conveyance of power to elements outside the enclosure.Even when a device is shielded, any imperfections in the shielding canrender the device susceptible to the action of EM waves.

BRIEF SUMMARY OF THE INVENTION

In this regard, the present invention provides an apparatus designed todisable, destroy, or detonate any electronically or electricallyactivated explosive device inside cargo, containers, or baggage intendedfor shipment, opening or inspection. An EM wave generator such as amagnetron, klystron, gyrotron, vircator, pasotron or similar highintensity EM wave generator is placed in proximity of the items to beinspected. Details of vircator (virtual cathode oscillator) and pasotronoperation have been documented [3, 4]. It is anticipated that the itemsto be scanned would be moved on a conveyor to facilitate the inspectionprocess. Since the mechanism of action of the apparatus is either todisable, destroy, or to activate the explosive device, the generator, aportion of the conveyor, and any activation devices used in conjunctionwith the apparatus would ordinarily be enclosed within protectiveshielding to prevent damage to the expensive components of the EM wavegenerator or nearby personnel in the event that the induced voltagesspike sets off the explosive device. An embodiment of the device that isautomated would have the EM wave generator activated whenever a cargo orbaggage item passed the transmitter.

The operation of the invention is straightforward. Baggage and cargo orany item to be inspected is placed on the conveyor belt of the inventionat some point before it is handled, opened, or loaded for shipment. Thecargo or baggage passes into proximity to the transmitter and triggersthe sensor, which, in turn, activates the RF or microwave generatorirradiating the cargo for a pre selected time. The RF or microwaves actto either destroy the electronics or wiring of the device so that itbecomes inoperative and therefore safe to ship or handle, or they act todetonate the device on the conveyor belt, eliminating the possibility ofan explosion during transportation. Microwaves and RF are typicallytransmitted by a number of materials such as plastics, cloth, wood,leather, resulting in little or no heating so that the only interactionis with metallic objects that act as receiving antennas. Many metalobjects will pick up the radiation and have voltages induced in them,but no significant damage is expected. It is the electronic componentsthat are uniquely sensitive to imposition of voltage spikes.

It is an object of the invention to provide a means of protection forhuman life and property by disabling or destroying electrical orelectronically detonated explosive devices. An application of theinvention would be for airport security, especially airline cargosecurity, which has been criticized as being particularly inadequate.Other applications include providing security in any environment where acontainer is received and is desired to be checked for the presence ofexplosive devices. Entities such as government offices, postal services,delivery companies, or military bases are examples where the inventionhas application. The use of this invention is for protection of humanlife and property through either destruction of the electronics orelectrical components of an explosive device, or through deliberatedetonation of the explosive device in a safe area instead where it wasintended for detonation.

It is anticipated that cargo would have to be specially marked if itcontained electronics, so that it could be searched by alternatemethods, manually, or by the current x-ray methods. The invention, to afirst approximation, is safe to humans, as human flesh isnon-conductive; however, the heating effects of some frequencies iswell-known so that the device would normally be expected to be shieldedto prevent exposure to personnel. The device provides a much faster andlower cost method of scanning cargo and baggage than present methods ofscanning, as a human operator is not required as an integral part of theoperation of the invention. The invention provides a dramatic reductionin searching time relative to existing screening methods, and permits asignificant increase in the total volume of cargo scanned for maliciousdevices.

Other objects, features and advantages of the invention shall becomeapparent as the description thereof proceeds when considered inconnection with the accompanying illustrative drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings which illustrate the best mode presently contemplatedfor carrying out the present invention:

FIG. 1 is a schematic diagram of the electromagnetic security apparatusof the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawing, the elements comprising a preferredembodiment of the electromagnetic security system of the presentinvention are shown schematically in FIG. 1. In reference to FIG. 1, ina preferred embodiment of the invention, the apparatus consists of aunit to generate high power RF or microwave radiation 1, a conveyor belt2 for moving the objects to be inspected into the proximity of the EMwave generator, a protective enclosure 3 made of metal or metal screen,to confine the EM waves to the interior of the enclosure and shieldpersonnel from the EM waves. A sensor 4 indicates when the position ofthe baggage or shipping container is within range of the transmittedradiation so that the radiation can be switched on. The sensor can beany of a mechanical switch, a light source and detector, acoustic sourceand detector or even an operator activated switch that senses thecorrect position of the baggage, cargo, or item to be inspected 5relative to the transmitter of the EM radiation. On receipt of a signalfrom the sensor, the EM wave generator is actuated to irradiate theobject on the conveyor belt. It is anticipated that since one outcome ofthe use of the invention is to detonate the explosive device, thatappropriate barriers would be built around the area of the transmitterto provide safety for nearby personnel in the event of an explosion.

In one embodiment of the invention a portable RF or microwave generatoris used in environments where a permanent installation is not warranted,or where a spot inspection is desired. The principle of operation of theportable invention is that same irrespective of whether it is fixed orportable. The shielding and method of transfer of the item to besearched is configured according to operator preference.

While there is shown and described herein certain specific structureembodying the invention, it will be manifest to those skilled in the artthat various modifications and rearrangements of the parts may be madewithout departing from the spirit and scope of the underlying inventiveconcept and that the same is not limited to the particular forms hereinshown and described except insofar as indicated by the scope of theappended claims.

1. A method for destroying or detonating electrical explosive devices hidden in objects being shipped or inspected, the method comprising: placing said objects onto a transport device; operating said transport device to move said object into a contained environment; and applying high levels of electromagnetic energy to said objects, wherein said electromagnetic energy interrupts circuitry within said electrical explosive device to destroy or detonate said device.
 2. The method of claim 1, wherein said electromagnetic energy is high power radio frequency radiation.
 3. The method of claim 1, wherein said electromagnetic energy is microwave radiation.
 4. The method of claim 1 wherein, said transport device is a conveyor belt.
 5. The method of claim 1, further comprising: detecting the position of said object within said contained environment before applying said electromagnetic energy.
 6. The method of claim 1, wherein said step of applying electromagnetic energy includes applying said electromagnetic energy using a portable electromagnetic energy generator.
 7. A device for destroying or detonating electrical explosive devices hidden in objects being shipped or inspected, the device comprising: a containment area; a transport device extending through said containment area, said transport device for transporting said objects into said containment area; and means for applying high levels of electromagnetic energy to said objects when said objects are within said containment area, wherein said electromagnetic energy interrupts circuitry within said electrical explosive device to destroy or detonate said device.
 8. The device of claim 7, wherein said electromagnetic energy is high power radio frequency radiation.
 9. The device of claim 7, wherein said electromagnetic energy is microwave radiation.
 10. The device of claim 7, wherein said transport device is a conveyor belt.
 11. The device of claim 7, further comprising: means for detecting the position of said object within said contained environment before applying said electromagnetic energy.
 12. The device of claim 7, wherein said means for applying electromagnetic energy is a portable electromagnetic energy generator. 